With the digital revolution, there is an unprecedented explosion in the volume of data to be processed, and the documents in use are more and more often of the multimedia type, i.e. they make use simultaneously and interactively of a plurality of different modes of representing information: still or animated images, sounds, texts, photographs, video signals, animated vector graphics, . . . .
Various methods are already known for compressing data. Nevertheless, when all of the information contained in a multimedia document is compressed, the volume of data to be processed remains considerable, not only when the processing consists in archiving, but above all when it consists in comparing a plurality of multimedia documents in order to find particular information included in said multimedia documents.